Conventionally, this type of heat exchange cooler includes an internal air passage for sucking the internal air of a heat generating element storing box, passing the sucked air through a heat exchanging element for the purpose of heat exchange, and again, returning the air into the heat generating element storing box, thereby circulating the air. The heat exchange cooler also includes an outside air passage for collecting the outside air, passing the collected air through a heat exchanging element for the purpose of heat exchange, and again, discharging the air outside. These air passages are separated by a partition plate and independent of each other, and each of the air passages internally includes a fan for transferring the air. This type of cooler is commonly known (for example, Unexamined Japanese Patent Publication No. 2001-156478).
Generally, a heat exchange cooler having such a configuration is used for cooling a cellular phone base station or the like, and low voltage DC power converted from commercial power is supplied from main body side of the cellular phone base station to the heat exchange cooler for the purpose of driving a fan or the like mounted with a DC motor.
The operation of conventional heat exchange cooler 100 will be described with reference to FIG. 17. As shown in FIG. 17, the air heated in heat generating element storing box 101 (hereinafter called inside air) is sucked from inside air suction port 102 of heat exchange cooler 100 by means of indoor fan 104 mounted with indoor DC brushless motor 103, and passed through heat exchanging element 105, and again returned into heat generating element storing box 101 from internal air discharge port 106, thereby forming a circulation passage.
On the other hand, the outside air sucked from outside air suction port 109 by means of outdoor fan 108 mounted with outdoor DC brushless motor 107 is passed through heat exchanging element 105, and again discharged outside from outside air discharge port 110. The inside air passage and the outside air passage are separated from each other by partition plate 111 in a state of being generally air-tight so as to be independent of each other, and at the intersection of the inside air passage and the outside air passage is disposed heat exchanging element 105 for exchanging sensible heat of the outside air and inside air. Heat exchange cooler 100 collects the low-temperature outside air, and performs heat exchange with the hot air in heat generating element storing box 101 by means of heat exchanging element 105, thereby discharging the warmed outside air and feeding the cooled air into heat generating element storing box 101.
Also, indoor DC brushless motor 103 and outdoor DC brushless motor 107 are usually equipped with a pole sensor such as a Hall element. Electronic control unit 112 as a controller for driving and controlling these indoor DC brushless motor 103 and outdoor DC brushless motor 107 is installed in the inside air passage of heat exchange cooler 100 to as to be free from the influence of low-temperature outside air or dust in a place where the base station is installed, and is connected to outdoor DC brushless motor 107 exposed to the outside air by using long relay power lead 114 and sensor signal lead 115. Driving power is supplied to electronic control unit 112 as a controller from relatively low voltage DC power 116 (see FIG. 20) installed in heat generating element storing box 101 or the like.
In such a conventional configuration, when heating in heat generating element storing box 101 is less and the outside air temperature is low, a heat exchange rate due to heat exchanging element 105 lowers, so that outdoor DC brushless motor 107 disposed at the outside air passage is often exposed to the low-temperature outside air. Accordingly, when a magnetic sensor such as a Hall element is installed in DC brushless motor 107, it is necessary to install heat exchange cooler 100, for example, in a place where the ambient temperature is higher than −30° C. so that the magnetic sensor is reliably operated. Also, since outdoor DC brushless motor 107 and electronic control unit 112 as a controller disposed at the inside air passage side are connected to each other with a long relay lead, there exists a fear of faulty operation of signal lead 115 for sensor signal as it is affected by noise. Also, the internal wiring of heat exchange cooler 100 is complicated taking much time for the work, and a problem of high costs for heat exchange cooler 100 arises.
A power circuit driving device used for heat exchange cooler 100 will be described in the following. Conventionally, a power circuit driving device using switching power based on a high-frequency switching system is commonly known as a power circuit driving device of this type. It is described with reference to FIG. 18, FIG. 19 and FIG. 20.
FIG. 18 shows heat generating element storing box 101, and heat exchange cooler 100 for cooling heat generating element storing box 101. Also, FIG. 19 shows heat exchange cooler 100, heat exchanger 105 as a heat exchanging means for discharging the inside air heat into the open air, electronic control unit 112 as a controller mounted with a microcomputer, and DC fan motor 119 driven and controlled by electronic control unit 112. Also, inside air passage flow N19 and outside air passage flow G19 are shown in the figure.
Also, as shown in FIG. 20, DC power 116 supplied from heat generating element storing box 101 (see FIG. 17, FIG. 18) is the voltage source of heat exchange cooler 100, and DC voltage is also supplied to electronic control unit 112 and DC fan motor 119. Also, heat exchange cooler 100 is supplied with AC voltage from commercial AC power source 122 as auxiliary power supplied from heat generating element storing box 101. The supplied AC voltage is connected to switching power source (AC/DC) 124 based on a high-frequency switching system for converting AC voltage to DC voltage via noise filter (N/F) 123. Specified DC voltage converted to DC voltage is collected from the output side of switching power source (AC/DC) 124, and the collected DC voltage is supplied to electronic control unit 112 and DC fan motor 119.
In the above configuration, as to DC power 116 as main power usually supplied, for example, even when DC power 116 is not supplied as a result of activation of DC power breaker (not shown) of heat generating element storing box 101, power will be continuously supplied from commercial power source 122. In this way, DC fan motor 119 is driven according to the instruction of electronic control unit 112 with the predetermined DC voltage converted by switching power source (AC/DC) 124. Thus, the outside air and the inside air are circulated, discharging the inside air heat into the outside air, in order to cool heat generating element storing box 101.
Also, as a power circuit driving device used for a heat exchange cooler of this type, commonly known is the one provided with a selector switch and a plurality of taps at the primary side of a commercial power transformer in order to cope with so-called 200V type commercial power, ranging from 200V to 250V in nominal voltage used in many countries and districts in the world.
The power circuit driving device used for the heat exchange cooler is described in the following with reference to FIG. 21. As shown in FIG. 21, commercial power source 122 as auxiliary power supplied to heat exchange cooler 100 from heat generating element storing box 101 is connected with select switch 120 for switching to nominal voltage (generally 200V, 208V, 220V, 230V, 240V, 250V). Select switch 120 is provided with, for example, six taps in order to cope with the levels of nominal voltages disposed at the primary side of commercial power source 121. DC voltage rectified and smoothed by the first diode bridge 117 and the first capacitor 118 is generated at the secondary side output of commercial power source 121. The DC voltage is supplied to electronic control unit 104 and DC fan motor 119.
In this configuration, in the installation of heat exchange cooler 100 is installed, when the knob of select switch 120 is turned to make the adjustment to the level of nominal voltage of commercial AC power source 122, the contact of select switch 120 is manually connected to a tap suited for the rated voltage of commercial power source 122 of commercial power transformer 121, thereby making a predetermined DC voltage. Here, even when no DC voltage is supplied, for example, because of activation of a breaker (not shown) of heat generating element storing box 101, DC power source 116 usually supplied as main power is supplied from commercial power source 122. Accordingly, DC fan motor 119 can be operated according to the instruction of electronic control unit 112 with predetermined DC voltage V1. Thus, the outside air and the inside air are circulated, the inside air heat is discharged into the outside air, and thereby, heat generating element storing box 101 is cooled (see FIG. 17, FIG. 18).
In the case of a power circuit driving device for a conventional heat exchange cooler using such a switching power source based on a high-frequency switching system, a problem that high frequency electric waves of noise are continuously radiated during the switching operation arises. In a heat generating element storing box for communication equipment, continuously radiated high frequency electric waves of noise must be reduced to such a level that the communication is not affected. For example, in 800 MHz band of cellular phone communication frequency, according to the limit value of interference waves of technical information equipment, CISPR (International Special Committee on Radio Interference) 22, there is a fear of trouble with the equipment when the level exceeds 37 dB μ V/m in a 10 m method, and it is required to be greatly lower than the level.
Also, in a type compatible with multiple power sources, the input voltage of switching power source is generally in a range form 90V to 264V. Taking into account ±10% of voltage variation of 200V type commercial power whose nominal voltage ranges from 200V to 250V, it is required to cover a range of 180V to 275V.
Also, in a power circuit driving device used for a conventional heat exchange cooler using a select switch for switching a plurality of taps at the primary side of the commercial power transformer, it is necessary to manipulate the select switch in accordance with the nominal voltage of commercial AC power supplied by the person in charge of installation during the installation work, and a problem of increase in man hour for the installation work arises. Consequently, it is required to reduce the man hour for the work.
Also, when a power circuit driving device is installed in a heat exchange cooler, a problem of wrong setting of the select switch, and it is desired to prevent occurrence of human errors arises.
Also, in case a commercial AC power is supplied, for example, exceeding the range of ±10% of nominal voltage due to a trouble with the distribution equipment or the like, a problem that the DC voltage output exceeds the specified range in case of fixed tap connection arises. Accordingly, it is required not to exceed the specified DC voltage even in case the commercial AC power exceeds the range of ±10% of nominal voltage due to a trouble with the distribution equipment or the like.